* {
	margin: 0;
	padding: 0;
	box-sizing: border-box;
}

#container {
	width: 420px;
	height: 420px;
	margin: 100px auto;
	position: relative;
}

.row {
	width: 420px;
	height: 140px;
}

.row .cell {
	float: left;
	text-align: center;
	line-height: 140px;
}


.row .cell:nth-child(1) {
	width: 140px;
	height: 140px;
	border-bottom: 10px solid #ccc;
	border-right: 10px solid #ccc;
}

.row .cell:nth-child(2) {
	width: 140px;
	height: 140px;
	border: 10px solid #ccc;
	border-top: 0;
	border-left: 0;
}

.row .cell:nth-child(3) {
	width: 140px;
	height: 140px;
	border-bottom: 10px solid #ccc;
}

.row:last-child .cell {
	border-bottom: 0;
}

.x::before {
	content: 'x';
	color: aqua;
	display: inline-block;
	width: 80px;
	height: 80px;
	font-size: 80px;
	line-height: 1;
	margin-top: 20px;
}

.o::before {
	content: 'o';
	color: purple;
	display: inline-block;
	width: 80px;
	height: 80px;
	font-size: 80px;
	line-height: 1;
	margin-top: 20px;
}

.w {
	display: none;
}

.win {
	position: absolute;
	width: 420px;
	height: 420px;
	background-color: rgba(0, 0, 0, 0.3);
	top: 0;
	left: 0;
	display: flex;
	flex-direction: column;
	align-items: center;
	justify-content: center;
}

.win p {
	width: 200px;
	height: 100px;
	margin: 0 auto;
	font-size: 40px;
	font-weight: 700;
	color: #fff;
	text-align: center;
}

.win button {
	width: 100px;
	height: 60px;
	color: #333;
	font-size: 40px;
}

.demo::before {
	content: 'x';
	position: absolute;
	top: 0;
	left: 0;
}